Planning for Risk: The Evolution of Water Supply Management

The water industry, and specifically the water supply and management practice, has evolved from a focus on cost-effectiveness, to the incorporation of sustainability principles, to formal considerations of risk and uncertainty in resiliency planning. Before describing this evolution and how we help our clients with their water supply management needs, it is pertinent to introduce an operational definition of “sustainability” and “resiliency.” Many people in the industry consider these terms buzzwords with marketing value and no solid meaning. But water supply planners and managers agree on these operational definitions:

“Sustainability” is the principle of serving our current needs without compromising the ability of future generations to serve theirs. And this is accomplished by considering economic, environmental and social elements in our management actions.

“Resiliency” is the ability of a system (physical, management, and government) to respond to shocks and bounce back to operational normalcy from those shocks, which can be man-made or natural.

From Cost-Effectiveness to Resiliency

Up until very late in the 20th century, decisions on how to invest in water supply infrastructure were based on relatively simple supply and demand studies. Studies followed a pure cost-effectiveness mindset and assumed that the recorded past would be a reliable measure of the future (what is called the “stationarity assumption”). Most importantly, when there was no gap between supply and demand under stationarity assumptions, the studies would conclude that there was no perceived need to further invest in the system. Under this approach, only the largest population centers had sufficient resources to formally address redundancy at the supply level, while other systems were left vulnerable to economic and natural shocks. Furthermore, many of the projects that were implemented carried unintended negative consequences for society and the environment.

Woodard & Curran was born in the early days of the Clean Water Act, when utilities started to face the need to internalize a lot of the environmental and social externalities during project planning. In the 1990s, as more and more of our nation’s cities and leaders bought into the mission of sustainability, the environment and society moved from being constraints to being an integral part of the decision-making process. And early in this century, a series of shocks—like hurricane Sandy, the most severe droughts ever observed in the southwestern United States, and the 2008 great recession—open the eyes of many utilities to the importance of implementing a risk assessment approach to supply and water resources planning. The mission to increase resiliency to unexpected events in our changing environment and complex social climate is more common today.

Resiliency in Context

Every water supply system faces different threats that can be addressed and mitigated by incorporating resiliency into long-term planning. For example, Marin Municipal Water District (MMWD) system in California, depends on surface water for most its water supply, which makes the district particularly vulnerable to drought. To address this issue, and other pressing concerns such as population growth, earthquakes, and wildfires, Woodard & Curran worked with MMWD to conduct a long-range water resources analysis for the district to address the vulnerability of their water resource system.

The primary analytical tool we used to assess vulnerability was a model developed in GoldSim. The model is systems-based tool which develops a big picture, low resolution snap shot of an entire water system and its influences—giving users the ability to focus on a set of related elements and their interactions and answer a variety of questions concurrently. With the model, MMWD can quickly evaluate the responses of the water resources system.

The GoldSim model simulates the district’s entire supply system—including pump stations, water mains, seven reservoirs, two treatment plants, a recycled water facility, and imported water supply—under a variety of conditions. To begin, we developed hydrologic models that took the likelihood and extent of future water supply shortages. From there, we identified and analyzed innovative approaches the district could implement to increase reliability under a wide range of scenarios. These solutions included increasing indirect potable reuse/direct potable reuse (IPR/DPR) and water transfers.

In the end, the model helped the district answer questions about MMWD’s current supply system reliability and determined how MMWD’s supply system would react under a variety of future events like wildfires, earthquakes, extended drought, climate change, major water quality disruption, landslides and system shutdowns. The model showed that while the district didn’t need to import more water to keep the system in its safe yield. the system was vulnerable to a six-year drought. From the model, we could see that if the district were to expand its existing programs—like increase conservation and expand scope of watershed management—and start manage adaptively by exploring low infrastructure alternatives for conjunctive ground water use and track hydrologic conditions and demand patterns, the district would improve its resiliency under number of future conditions. Due the simple interface and the complex analysis available, the district has adopted the model and will continue to use it to update their safe yield for the system and to develop annual operation plans.

Sustainability, Still Relevant

While resiliency is, and will continue to be, at the forefront of many supply studies in United States, the concept of sustainability is still relevant and necessary. “Resiliency” is not the new buzzword, replacing “sustainability.” Using the sustainability framework to evaluate infrastructure projects to achieve economic, environmental and societal objectives is not only necessary but helpful in identifying resiliency measures. At Woodard & Curran, our experience clearly indicates that resiliency solutions often lead to multi-objective and multi-benefit solutions that tend to be decentralized and require stakeholder engagement and the active participation of societal actors. These solutions can be difficult to justify under a financial-only basis. When projects use a sustainability approach with its triple bottom line principles, solutions that incorporate resiliency and examine a wide range of scenarios are more likely to be supported for implementation by managers, the public and elected officials.